There is a conventional content and license distribution method for a content distribution system in which a content reproduction apparatus obtains, from a content distribution server, both a content and its license in which usage rules for allowing the use of the content are described, as single data. For example, a patent literature 1 (Japanese Laid-Open Patent Application No. 2000-155734 Publication) discloses a method for downloading content data and its license as single data from a content server.
It can be assumed in the future content distribution that a content is linked with another content and a content reproduction apparatus reproduces these contents in sequence according to the link. For example, it is assumed that a content which places a link to another content (a link source content) is a real time streaming content to be distributed according to the schedule, while a content linked from the link source content (a linked content) is a storage content which is previously downloaded to the content reproduction apparatus. It is further assumed that the license of the linked content is changed with the lapse of reproduction time of the link source content. For example, it is assumed that needs for such control may grow that although a user can reproduce the linked content only once if he/she reproduces the link source streaming content for only 10 minutes from the beginning, he/she can reproduce the linked content three times if he/she reproduces the link source content for another 10 minutes.
However, in the case where the license of a storage content is changed depending on the reproduction time of a real time streaming content to be distributed according to the schedule, as described above, the conventional method requires obtaining, from a content server, a content on which the license that varies depending upon the reproduction time of the link source content is multiplexed, which is likely to cause increase in access to the content server for obtaining such content. Furthermore, since such link source content is a real time streaming content to be distributed according to the schedule, it is likely that the accesses to the content server for obtaining the content concentrate in a specific period of time. As typically shown in the above-mentioned example, in the case where the license of a linked content is changed depending on a link source content, regardless of whether the linked content is a streaming content or a storage content, access to a content server for obtaining such content are likely to increase. So an object of the present invention is to provide a method for solving these problems.